The present invention generally relates to pumps. Specifically, the invention is a diaphragm pump especially useful for high pressure pumping applications.
Various diaphragm pumps for use in low pressure pumping applications are well known in the art. Generally, these diaphragm pumps move a transient fluid by displacing a diaphragm. The displacement of the diaphragm alternatelY draws the transient fluid into a pumping chamber and expels the transient fluid from the pumping chamber. One known means used for displacing the diaphragm involves the use of a pumping plunger. The pumping plunger, partially inserted into a motor chamber, is reciprocated. The movement of the pumping plunger alternately increases and decreases the pressure exerted by the hydraulic fluid in the motor chamber. Because the diaphragm partially forms the motor chamber, the diaphragm is displaced by the change in pressure exerted by the hydraulic fluid.
Heretofore diaphragm pumps have not been found well suited for high pressure pumping applications. One obstacle to using diaphragm pumps that incorporate a pumping plunger for high pressure pumping applications is the swift loss of adequate motor chamber pressures. This loss occurs because hydraulic fluid leaks from the motor chamber around the plunger seals. This leakage occurs when the hydraulic fluid in the motor chamber is highly pressurized to overcome the opposing pressures exerted by transient fluid on the diaphragm. The high pressures generated in the motor chamber force hydraulic fluid past the plunger seals. After sufficient hydraulic fluid leaks from the motor chamber, the pump is unable to develop the motor chamber pressures necessary for effective operation.
Heretofore, those skilled in the art have attempted to solve the leakage problem by changing the seals, the seal design or the pump design. None of these changes have proven completely satisfactory based on the considerations of effectiveness, cost and reliability.